Dynamic memory really makes it complicated, especially since support for it is apparently baked into the Windows Kernel. In general, my VMs are setup to have 512MB at boot, but able to shrink down to 320MB and generally grow upto 1-4GB depending on workload. I still use pagefiles, just of the smallest fixed sized which allows mini-dump files to be created (which for windows 2012, is ~840mb)

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I have no idea if this would be a good idea, but you could dedicate a virtual disk to paging, but thin-provision it to conserve space on the host?

Dedupe on a pagefile makes no sense. The only way you'll get any space savings is if the pagefiles from several Guests are in the same dedupe pool. Even then, the space savings will be minimal.

In a virtualized environment, we REALLY hate paging. It causes severe system performance problems - much worse than paging on a physical server. I'd do everything possible to keep the paging latency down, which means thick allocations and no dedupe. If you have a large SSD array to use for pagefiles, you can do thin allocations, but, in most circumstances, you'll do better putting the SSDs elsewhere.